Bending moment at one-way and two-way solid slab intersection

[hoshang]

Hi,
please find the attached file. The gridlines are as follow:
X: 0,4,4,4,8m
Y: 0,5,5
The picture displays moment isolines for gravity loads for DL and LL ultimate combination. Is it reasonable to have as much as 58.5 (metric units) at one-way and two-way solid RC slab intersection? And why?

 

[hoshang]

Hi all,
any thoughts would be highly appreciated.

 

[Celt83]

The concrete doesn't care what you are calling one-way or two-way it will span based on stiffness which will be influenced by the reinforcement layout. If you don't reinforce for the moment at the interface the slab will crack and the joint will soften leading to larger deflections than your model currently predicts.

 

[hoshang]

The concrete doesn't care what you are calling one-way or two-way it will span based on stiffness

If one adds beams as in the attached image (red lines), will this redistribute the moment more evenly?

it will span based on stiffness which will be influenced by the reinforcement layout.

Do you mean I can change the reinforcement layout such that it will redistribute the moment evenly? How?

 

[HTURKAK]

It is not reasonable..
I do not know the software that you have used but if peak value 58.5 unit is kN-m, the average should be in the range of 20 kN-m.
You may check your software for unit width moment values or change the model.
I think you have modelled the slab with FEM plate elements and beam and columns frame , line elements . Literally the slab supported by point at column locations and you get very high moments .



He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[hoshang]

Hi HTURKAK,
Thanks for your response.
your quote from my OP doesn't seem reasonable.
Quote (hoshang
The picture displays moment isolines for gravity loads for DL and LL ultimate combination. Is it reasonable to have as much as 58.5 (metric units) at one-way an)

One should quote something such that it could be understood. Anyway,

I do not know the software that you have used

I use Autodesk Robot Structural Analysis (Celt83 practices it as well).

You may check your software for unit width moment values or change the model.
I think you have modelled the slab with FEM plate elements and beam and columns frame , line elements . Literally the slab supported by point at column locations and you get very high moments .

So, you think there's no effect if one combines one-way slab with two-way slab, don't you?

 

[HTURKAK]

The title of this thread (Bending moment at one-way and two-way solid slab intersection ). My point is , the concentrated moment 58.5 (metric units) is due to column modelling rather than one-way and two-way solid slab intersection . Remove column and see the difference.



He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[hoshang]

Hi Celt83,
your cooperation would be highly appreciated.

 

[Celt83]

See this thread: Link

Review these texts:
Structural Analysis - Kassimali
A First Course in the Finite Element Method - Logan
Finite-Element Design of Concrete Structures, 2nd edition - GA Rombach

 

[hoshang]

Hi Celt83,
In my case, the slabs aren't flat plate. Rather, they are supported by beams (have a look at the attached image in OP).

 

[Celt83]

The slabs are modeled as finite element panels, the panel will span based on stiffness of itself and supporting elements. The point support of the column is orders of magnitude stiffer than the beam, if no axial deformation of the column is considered then it is infinitely more rigid than the beam, so everything will tend to span to the interior column.

I strongly encourage you to study the three textbooks referenced in my earlier post. The Rombach book provides more advanced information that requires the foundational knowledge from the Kassimali and Logan texts.